Unitary heating device for supplying hot combustion gases and hot air



A. C. ALLEN UNITARY HEATING DEVICE FOR SUPPLYING Filed Sept. ll, 1952 HOT COMBUSTION GASES AND HOT AIR IIIIIIII IAI llllllllllllll l! Feb. 5, 1957 United States Patent O UNITARY HEATING DEVICE FOR SUPPLYING HOT COMBUSTION GASES AND HOT AIR Arthur C. Allen, Chicago, Ill., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application September 11, 1952, Serial No. 309,073

4 Claims. (Cl. 126-110) This invention relates to a novel hand tool which I refer t as a heater blowgun. In general the tool is adapted to be hand-held much like an electric drill or sander, for instance, and is adapted to have a high output of hot air and hot products of combustion which are useful for many purposes as will appear presently.

One of the objects of this invention is to provide a novel device which is light and compact and adapted to be hand-held and which can be manufactured at low cost, but which has a high output of hot air and hot products of combustion.

Yet another object is to provide a device of this general character which may be used for limited space heating, material heating, paint removal, radiator thawing, engine warm-up, manifold, crankcase or carburetor heating and the like.

Still another object is to provide a device of this general character which can supply hot gases at several different temperatures so as to adapt the device for a wide range of applications.

Still another object is to provide a novel heater blowgun having the characteristics set out above, which is adapted to be used in and around automotive vehicles for a variety of purposes and which may receive its only source of power from the vehicle battery without putting a heavy drain thereon.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention which is illustrated in the accompanying drawings.

In the drawings:

Fig. l is a somewhat diagrammatic, longitudinal vertical, sectional view through a heater blowgun of the type to which the present invention pertains;

Fig. 2 is a rear View thereof and may be considered as taken in the direction of the arrows along the line 2-2 of Fig. 1;

Fig. 3 is a transverse, vertical, sectional view which may be considered as taken in the direction of the arrows substantially along the line 3 3 of Fig. l; and

Fig. 4 is a diagram of the electrical circuit incorporated in the device.

From the drawing it will be seen that I have provided a long, horizontal, relatively slender, cylindrical sheet metal casing 10, which is equipped at one end with a handle 12 on the upper side thereof. The forward end 14 of the casing 10 is rounded so as to be partially closed and at the center thereof is provided with an outwardly projecting tubular spud 16 and a separate tubular outlet 18 projecting downwardly. The spud at the outlet 18 is provided with side pins 20 which operate in bayonet slots 22 of a cup shaped cap 24 adapted to fit over the outlet opening 18. Thus the opening 18 can be either open or closed as desired for a purpose to be pointed out presently.

- The handle 12 is formed of sheet metal or as a light metal casting and has a hollow space or passage 26 exice tending therethrough. The forward end of the handle is attached to the housing 10 near the rearward end thereof and the passage 26 at its forward end communicates with the space therein. The rearward end of the hollow handle 12 has the passage 26 communicating with the outlet 28 of a small centrifugal blower housing 30 having a rearwardly opening air inlet passage 32. Within the housing 30 there is a centrifugal blower wheel 34 mounted upon the shaft 36 of a small electric motor 38. This motor is horizontally disposed and enclosed within a tubular shell 40 arranged directly behind the rearward end of the cylindrical housing 10 and separated therefrom by a partition 42. With the motor 38 energized, therefore, air is taken into the center of the blower wheel 34 and driven outwardly so as to pass through the hollow space 26 within the handle 12 and thence into the rearward end of the housing 10 at the top thereof.

A cylindrical shell or burner tube formed of stainless steel or similar material 44 is axially aligned within the casing 10 and has its rearward end closed against the partition 42 such as by welding for instance. The upper surface of the burner tube 44 has small openings 46 therethrough which in the present instance are in alignment with the outlet opening of the hollow handle 12, so that air flowing forwardly through the passage 26 can pass partially into the openings 46 and partially into the annular space formed between the axially aligned burner tube 44 and casing 10.

At its forward end the inner combustion tube 44 is necked down as at 48 so as to pass through the spud 16 to which it is sealed in comparatively tight relation. A portion extends beyond the spud 16 for a short distance so as to form an adapter 50 to which a desired length of exible metal hose 52 may be attached as by the clamping band 54.

At its rearward end the tube 44 encloses a burner S6 the outlet end 58 of which is fitted to the central opening of an annular ring 60 the exterior of which lits the tube 44. The ring 60 and the wall 42 together with the portion of the tube 44 between the ring and the wall forrn a plenum chamber around the burner 56. The ring prevents communication between the plenum chamber space within the combustion tube 44 to the'rear thereof and the space within the tube forwardly of the ring, excepting by way of passages through the wall of the burner 56. The burner may be of any suitable type but the one shown has openings 62 through its wall at the rearward upper portion thereof through which air for combustion can reach the inside of the burner 56. It also has a plurality of dilution air holes 64 which surround the burner 56 somewhat forwardly of the principal openings 62, but rearwardly of the annular ring 60. Near its center, the burner is necked in somewhat to retain liquid fuel in the rearward portion.

A hot wire igniter of any suitable type is .indicated at 66. It is threaded through the partition 62 so that its ungrounded terminal is within the moto-r housing 40 while the incandescent end lies within the combustion chamber 56. The igniter terminal indicated at 68 is connected by a wire 70 to one terminal of a push button electric switch 72 mounted upon the underside of the forward portion of the handle 12. The other terminal of this switch is connected by a lead 74 which lies within the hollow handle 12 to a junction point 76, from which one lead extends to the ungrounded side of the motor 33, while another lead '78 forms one of the members of the power cord 80. The other member of this power cord is grounded to the device at any suitable point as indicated at 82. Whenever the cable is ,energized by being connected as by clips directly to the automobile battery or by a plug adapted to t the ordinary cigarette lighter socket, the motor 38 will be placed in operation and the igniter 66 will be energized whenever the push button 72 is held depressed.

The motor housing V40 is `enclosed within a separate housing S4 so as to provide space betweenthe two, .the lowerportion thereof servinguas a fuel tank. Within this lower portion there is provided a small 'hand pump .86 screwed into an opening at the back. This pump is of the type used on blowtorches or `gasoline lanterns, kby means of which an operator can create a superatmospheric pressure within the tank indicated generally by the numeral .88. Directly opposite the pump, at the front of the tank, there is a fuel control needle valve 90. .T his needle valve has a control knob 92 and an-inlet tube V94 extending into a position near the bottom of the tank 88. Its outlet tube 96 leads to the burner 5d.

rl`he device .is used in the following manner. The pumpis unscrewed from the tank 38 and a quantity of suitable fuel, gasoline for instance, is poured into the tank. The pump 86 is then replaced and by depressing its knob several times the pressure within the tank can be raised to an appropriate level. The power cord 'Sil is then connected to a suitable source of electric power, such as an automobile battery for instance, thereby placing the motor 38 in operation. The igniter button '72 is then depressed and the knob 92 turned so as to permit fuel from the tank 8) to llow through the control valve 9) and thence to the burner 56.

Under these conditions the burner 56 will receive fuel through the tube $6 and air for combustion by way of the hollow handle 12, the openings 46, and burner air inlet 62. The igniter being hot will ignite the gas and air mixture within the burner 56, after which the igniter switch 72 may be released. The mixture formed within the rearward portion of the burner 56 will be relatively rich since this is advisable for insuring ready ignition land steady operation. This burning rich mixture is diluted somewhat by additional air entering `through the openingsV 64 so as to produce a hotltiame, much like that ofa blowtorch, which is projected into the interior of `the .burner tube 44 through the burner outlet 58.

These hot products of combustion pass down the tube as indicated by the arrows and through the necked down portion 4S 'and thence into the flexible metallic hose S2. Just before they enter the necked down portiont48 vthese products of combustion pass through a cylindrical plug 98 formed of a material having relatively good heat conductivity, such as copper for instance. This plug is drilled longitudinally with a `plurality of holes 100 such that it acts as a flame arrester. Its function is to prevent any possibility of the hot products of combustion from the heater igniting a gas and air mixture within thespace occupied by the heater or into which Ithe hose 52-extends.

The major portion of the air from the blower flows forwardly through the annular space between the hot combustion tube 44 and the external shroud 10 so as to leave by way of the downwardly projecting spud 18. The hot air leaving the spud 18 therefore contains no products of combustion and can be used for space heating, whereas the exhaust products passing through the exible hose 52 can be arranged to enter the atmosphere at a point `outside* of the space to be heated.

V-If the device is used by an automobile mechanic who needs to work within a relatively small enclosure in cold weather, for example, within a truck cab, the deviceof the invention can be placed within the cab with theA hose 52 extending to the outside through some available opening. Such an opening can be specially provided for the purpose, or one of the truck doors or one of the windows can be left slightly open so as to provide room for passage ofV the'hose 5 2. In any event the hot productsof cornbustion'exhaust outside the cab, whereas' hot v entilating airforfheatingthe spacel to a comfortableI temperature `leaves the device by way of the outlet opening 18.

If the device is to be used in applications where a very high temperature is desired, such as paint removal for instance, ory perhaps transmission thawing or for some similar need, the cap 24 can be used foclosing the hot air opening 18 thus forcing all of the air from the blower 3d through the burner 56 inasmuch as none of this air passes through theventilating y'air space between the burner tube 44 and the shell 10. Under these conditions, since more combustion air is available, the control valve 92 can be opened to a greater extent so as to supply a larger quantity ci fuel to'theburner 56 and thus theheat output of the burner is greatly increased. Further, since the hotproducts of combustion from the burner' are not cooled by heat exchange to a Ventilating air stream, these hot products leave the -outlet opening 50, or the outlet of the flexible tube 52 if it is used, at an extremely high temperature. The device can be held by the handle 12 to direct these hot gases where desired. Of course intermediate temperatures can be arrived-at by leaving the cap 2.4 oit the ventliating air outlet opening 18 and simply using the hot products of combustion for the tube 62, although ordinarily greater heating efficiency is of course achieved by closing the Ventilating air outlet opening in the manner described. l

From the above it will be seen that the heater blowgun of thepresent invention can b e manufactured at low cost, is safe and not complicated in operation, uses only a small amount of electric power, andyet is easy to manipulate and carry about and has a high heat output. It may, as explained, be used for space heating or, if desired, for the purpose of raisingsurface temperatures to a high level; in other words, muchl in the vmanner of a blow torch but with fiar greater safety because the llame arrester 98 prevents the possibility of the vdevice igniting combustible vapors in the vicinity of the device.

Having described my invention, what'I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. Along slender heating device adapted to be held in the hand of an operator and having a handle secured to the upper side adjacent the rear end thereof, said handle being hollow, said device havingan electric motor driven blower, a burner, a heat exchanger having gas and Ventilating air passages therein, a fuel tank, means including a control valve for supplying fuel to said burner from said tank, ignition means for said burner, means forming separate outlet openingsfor the gas and ventilating air passages of said heat exchanger, said device having passages formed therein leading from said blower by way of said hollow handle to said burnerand thence to said gas passages and also directly from said hollow handle to said Ventilating air passage of said yheat exchanger, manually operable means for obstructing the flow of air through said Ventilating air passages so as to cause substantially all of the air from said blower to pass through ,said burnerand gas passages, and said motor, said blower, said tank and said; burner beingdisposed substantially below said handle, nsaid'heatexcl'ianger extending outwardly away'from said burner and` handle, and said outlet openings being at` the end of said heat exchanger remote fromsaid handle.

2. Afheatingv device adapted to be held in the hand, said"device,comprisi ngaunitary self-supporting structure providing a pair of outlets vat oneend thereof, lmeans forming-a heat exchanger having a-combustion products passage connected to one of said outlets and'having a Ventilating air passage connected tothe other outlet, means forming a-combustionchamber connected to said combustion products passage to supply -hot products of combustion theretonn'eans including a fuel 'tank for supplying fuel to said combustion chamber, a blower, a hollow carrying handle on the device, the'passage through said hollow handle constituting an air duct, said air'duct -being connected for'conveying airunder pressurefrom said blower to said'ventilating air passage and tosaid combustion chamber, ignition means for said combustion chamber, said heat exchanger having a relatively small heat transfer capacity as compared to the heat output of said combustion chamber, so that only a relatively small portion of the heat available in the products of combustion is absorbed by the Ventilating air, whereby both hot Ventilating air and hot combustion products may be utilized simultaneously for heating purposes under conditions where contamination of the heating medium by products of combustion is to be avoided and where such contamination is unimportant.

3. A long slender combustion heating device adapted to be held in the hand of an operator and comprising, in combination, an elongated heat exchanger deiining Separated passages extending therethrough from end to end thereof for combustion gases and for unburned air, a hollow handle connected to one end of said heat exchanger and extending upwardly and rearwardly beyond said one end in general overlying relation to the extended axis of the heat exchanger, a rotary blower, means connected to said one end of said heat exchanger and supporting said blower near the end of said handle remote from said heat exchanger, a liquid fuel tank mounted in generally underlying relation to said handle, a burner mounted at said one end of said heat exchanger and communicating with said combustion gas passage therein, means including a control valve for supplying fuel from said tank to said burner, ignition means disposed in association with said burner, said handle forming an air supply passage extending therethrough from said blower to said one end of said heat exchanger, means connecting the heat exchanger end `of said air supply passage to the adjacent end of said heat exchanger passage for air to be heated, and means providing communication between said heat exchanger end of said air supply passage and said burner to provide for a iiow of air from said air supply passage through said burner into said heat eX- ehanger passage for combustion gases, and means on the end .of said heat exchanger remote from said handleV forming separate outlet openings from said heat exchanger passages for combustion gases and for heated air.

4. A hand gun for delivering a stream of hot combustion products and a stream of unburned air heated by combustion in the gun and comprising, in combination, a lightweight structure adapted to be held in one hand and including an elongated heat exchanger, said heat exchanger defining a central combustion gas passage extending longitudinally therethrough and an annular passage for air to be heated extending longitudinally through the heat exchangerv in surrounding relation to said combustion gas passage, a burner mounted at one end of said heat exchanger and connecting with the adjacent end of said combustion gas passage, means forming a plenum chamber around the burner communicating through the burner with said combustion gas passage, said lightweight structure including a liquid fuel tank adjacent said burner, means dening a fuel supply passage extending from said fuel tank to said burner, a blowersupported on said lightweight structure in adjacent spaced relation to said one end of said heat exchanger, said lightweight structure including means dening an air supply passage connecting said blower with said one end of said heat exchanger, said heat exchanger i, end of said air supply passage opening into the adjacent end of said annular air passage in spaced perpendicular relation to said plenum chamber means, said plenum chamber defining an air inlet to the chamber opposing the adjacent end of said air supply passage in direct alinement therewith, means on the end of said heat exchanger opposite said burner communicating with said central combustion gas passage and defining an outlet therefrom, a haine arrester mounted at the outlet end of said combustion gas passage to prevent flame from reaching said combustion gas outlet, and means on said heatV exchanger end opposite said burner communicating with said annular air passage and defining an outlet therefrom separate from said combustion gas outlet.

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